- init processing provider correclty to allow reloading of plugin
- fix processing progress bug when called without gui
see https://gis.stackexchange.com/a/250134
- log client errors to console when not using QgsMsgbar

fixes #39
adds an option to..
- dissolve isochrones of the same range to a multipolygon
- make the polygons non-overlapping
also fixes an issue with file based output.
also makes the range param a text input, which is easier to use.